I, too, have been keeping my tracks as GPX files, from Bora Bora to Cinque Terra...
TrailRegistry.com and GPXchange.com are good sites, but not much traffic.
LocalHikes.com has quite a bit of stuff, but they aren't accepting new Reporters and there isn't as much near my home as I'd like.
http://www.localhikes.com/ is fee based and it feeds National Geo ->
http://www.trailsillustrated.com/topo/search.cfm which won't let you upload...
IT SURE WOULD BE NICE IF Groundspeak WOULD LET PEOPLE UPLOAD THESE SORTS OF FILES!